I have heard good things about Sota, by 2tuff, steve555 and others. All the ones I recommended are AC powered, the Sota has the option of battery powered which could be convenient. The latter one you mentioned I have no idea on and the bi-directional electrodes are new to me and they admit is still being researched so I don't know the advantages/disadvantages of that. Sounds like marketing.
Use your gut in deciding.